Soy sauce is produced through mixing of steam-boiled soybeans and roasted and milled wheat, inoculation and culture of a seed koji mold for soy sauce therein to result in a soy sauce koji, addition of an adequate amount of an aqueous common salt solution to prepare moromi (a kind of mash), formation of mature moromi via fermentation and maturation for a certain period of time, press, filtration, pasteurisation (sterilzation), and clarification.
It is known that the thus obtained soy sauce contains 250 or more types of aroma components such as flower and fruit aroma components and aroma components from a variety of liquors and vinegars. Differences in types or amounts of such aromas characterize the soy sauce aroma. Soy sauce generally contains alcohols that constitute soy sauce aroma components at concentrations of 2% to 3%. It is known that such alcohols facilitate the heat cooking of food materials and enliven aroma components (see, for example, Non-Patent Literature 1).
In addition, among the above alcohols, ethanol, 2-phenyl ethanol, isobutyl alcohol, isoamyl alcohol, and the like are known as aromatic components having favorable influences on soy sauce quality (see, for example, Non-Patent Literature 2).
In particular, it is known that 2-phenyl ethanol has a rose-like aroma and thus it is an important aromatic component contained in soy sauce (see, for example, Patent Literature 1).
Therefore, soy sauce production methods for producing brewed soy sauce containing the above alcohols at high concentrations have been studied.
It is well known that succinic acid is an umami (pleasant savory taste) component contained in shellfish and the like. It is also known that succinic acid is generated during soy sauce brewing and serves as a taste component having favorable influences on soy sauce quality (see, for example, Non-Patent Literature 2).
Meanwhile, the growing interest in health has boosted the popularity of food with reduced common salt in recent years. Accordingly, the demand for low common salt soy sauce has been increasing in the soy sauce market. Also, there is large demand for low common salt soy sauce powders used in the market for condiments for professional use and processed foods.
Hitherto, various low common salt soy sauce production methods have been examined. Examples of such methods include: a method comprising using water in which potassium chloride has been dissolved instead of an aqueous common salt solution; a method comprising using an aqueous low-concentration common salt solution to which ethanol has been added instead of an ordinary aqueous common salt solution; a method comprising using a raw soy sauce instead of an aqueous common salt solution to produce a thick soy sauce and diluting the thick soy sauce with water in the final step; and a method comprising desalting soy sauce using an ion-exchange membrane or a particular resin.
In addition, there is a known method comprising keeping the common salt concentration in soy sauce moromi at a low level of approximately 10 w/v % (i.e., the percent (%) of common salt in moromi juice) and providing certain conditions that prevent proliferation or survival of so-called spoilage bacteria that cause spoilage of moromi so as to prevent spoilage; that is to say, a method comprising keeping the moromi temperature at 40° C. or more (e.g., 55° C. in an extreme case) by heating. In general, spoilage bacteria are weakened under acidic conditions. In this regard, there is a known method for preventing proliferation of spoilage bacteria by adding an acid such as hydrochloric acid or lactic acid to moromi and keeping the pH at 4.0 or less (e.g., 3.0 in an extreme case). For example, Patent Literature 2 teaches that it is possible to prevent spoilage of moromi in the maturation phase during production of an alcohol-containing condiment by adding lactic acid to moromi so as to keep the pH at 4.5 or less, and preferably at 3.5 to 4.2.
However, the above methods require using special means. This inevitably results in flavor deterioration. In such cases, it is difficult to obtain a low common salt soy sauce or soy sauce powder having a more satisfactory aroma and taste than conventional brewed soy sauces. In view of the above, establishment of a method for producing a low common salt soy sauce having a favorable flavor has been awaited.
Meanwhile, conventional soy sauce powders are likely to become hygroscopic and deliquescent and thus they easily form powder blocks during storage. In addition, such soy sauce powders are disadvantageous in that they are more likely to become sticky and thus they are less likely to be uniformly mixed with other powder components.
A conventionally known method for overcoming such disadvantages of dried and powderized soy sauce is a method comprising: adding water or an aqueous common salt solution to moromi after alcohol fermentation (i.e., soy sauce moromi obtained within a period from the 40th day after the start of production to immediately before press) so as to result in a concentration of 13% (w/w) or more, adding soy sauce yeast thereto, and carrying out culture to adjust the direct reducing sugar concentration in soy sauce moromi juice or soy sauce to 1.5% (w/v) or less (Patent Literature 3).
However, no method for overcoming the aforementioned disadvantages of soy sauce powders without using special means so as to obtain a soy sauce powder having a favorable flavor and containing 2-phenyl ethanol and succinic acid at high concentrations has been known.